The indirectly fired gas turbine uses clean air as working fluid. The GT compressor increases both pressure and temperature of the working fluid, which is then further heated in the heat exchanger (HE) by the hot flue gases from a biomass (pellet or chip) furnace. The compressed hot air reaches the maximum cycle temperature by the natural gas internal combustion, then expands into the gas turbine, generating mechanical and then electrical energy through and electrical generator. In our scheme, a part of direct (natural gas) combustion is maintained, in order to achieve good thermodynamic efficiencies in the GT and to reduce thermal (lower max temperature) and corrosive (dilution of pollutant from biomass burning) stresses on the high temperature HE (800-850 °C). Previous works dedicated to this investigation concluded as this working condition is compatible with high quality steel. The energy in the exhaust flue gas (350-400°C) is recovered for heat and cold.

The plant is based on a small scale turbomachinery, which is commercially available and developed in EU. This kind of machines have very long service intervals and very good reliability. No major modifications (e.g. redesign of turbine or compressor blades) is considered in this project.
The externally fired gas turbine is totally isolated from the flue gas and any contaminants or particulates from biomass combustion.
The key developments in the application of this cycle are the high temperature HE, which will have to withstand contaminated biomass flue gas streams at high temperatures (~ 800-850 °C), the development of a specific control strategy for the whole BIO_MGT polygeneration plant, the adoption of a sophisticated low particulate emission bio-furnace.

The project addresses a niche but considerably large market by integrating fossil and renewable (biomass) fuels into a small scale (~100 kWe) innovative (first of its kind) polygeneration unit.

The proposed system will represent:

an economically viable

a technically reliable

an efficient

an environmentally friendly

an innovative

option for small scale cogeneration/polygeneration in buildings and industry.

This system is in perfect agreement with the targets established by the EC Directives on cogeneration, bioelectricity as well as the goals of the Kyoto Conference.

The Logo

The logo, specifically developed for the project communication, syntheses the characteristics of the BIO-MGT System. The green circle at the bottom is the Biomass heating the vector fluid (main air flow, inmultiple colors) that is going to evolve in the MGT. The blue circle quarter of ellipse is the natural gas that goes into the MGT, after mixing/burning with the main air flow.The Text is green for the BIO part and Black and Blue for the MGT part (representing the Natural Gas share).

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